U.S. patent application number 10/505467 was filed with the patent office on 2005-05-05 for device for the simultaneous, continuous measurement and regulation of the acetate and triacetine level in filter rods of the tobacco-processing industry.
Invention is credited to Gerlitzki, Manfred, Herrmann, Rainer, Sexauer, Wolfgang, Teufel, Eberhard.
Application Number | 20050096202 10/505467 |
Document ID | / |
Family ID | 27740286 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050096202 |
Kind Code |
A1 |
Teufel, Eberhard ; et
al. |
May 5, 2005 |
Device for the simultaneous, continuous measurement and regulation
of the acetate and triacetine level in filter rods of the
tobacco-processing industry
Abstract
The invention relates to a device for producing cigarette
filters, which comprises a conditioning section (AF) for
conditioning the supplied filter tows, a formatting device (F) for
producing a wrapped filter strand, a dosing device integrated into
the conditioning section for dosing a softener. The device further
comprises sensors that detect the mass flow of filter tow material
M1 and sensors that detect the sum of the mass flow from filter tow
material and softener compound M2. A measuring and regulation unit
is coupled with the sensors for measuring the mass flows (M1 and
M2) in such a manner that both the filter material and the softener
compound can be measured and regulated independently.
Inventors: |
Teufel, Eberhard;
(Gundelfingen, DE) ; Sexauer, Wolfgang; (Freiburg,
DE) ; Gerlitzki, Manfred; (Freiburg, DE) ;
Herrmann, Rainer; (Hamburg, DE) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Family ID: |
27740286 |
Appl. No.: |
10/505467 |
Filed: |
December 2, 2004 |
PCT Filed: |
February 21, 2003 |
PCT NO: |
PCT/EP03/01821 |
Current U.S.
Class: |
493/39 |
Current CPC
Class: |
A24D 3/022 20130101;
A24D 3/0295 20130101 |
Class at
Publication: |
493/039 |
International
Class: |
B31C 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2002 |
DE |
10207357.0 |
Claims
1. A device for producing cigarette filters, comprising a
conditioning section (AF) for conditioning supplied filter tows, a
formatting section (F) for producing a wrapped filter strand, and a
dosing device (4) integrated into a conditioning section for dosing
a softener, wherein the device further comprises sensors that
detect mass flow of filter tow material M.sub.1 as well as sensors
that detect a sum of the mass flow from filter tow material and
softener compound M.sub.2, and wherein the device comprises a
measuring and regulation unit that is coupled with the sensors for
measuring the mass flows (M.sub.1 and M.sub.2) in such a manner
that both the filter material and the softener compound can be
measured and regulated independently.
2. The device pursuant to claim 1, wherein the device, when viewed
in the moving direction of the filter strand, in front of and after
the dosing device (4), for the softener sensors (S.sub.m1;
S.sub.m2) that detect the length-related mass m.sub.1, m.sub.2 of
the continuous filter strand and sensors (S.sub.v1; S.sub.v2) that
detect the current speeds v.sub.1 and v.sub.2 of the continuous
filter strand are provided, wherein the respective mass flow
results from the products of m.sub.1.times.v.sub.1=M- .sub.1 and
m.sub.2.times.v.sub.2=M.sub.2.
3. The device pursuant to one of the claim 2, wherein the sensor
(S.sub.v1) that detects the speed v.sub.1 and the sensor (S.sub.m1)
that detects the length-related mass m.sub.1 are arranged directly
adjacent.
4. The device pursuant to claim 2, wherein the sensors (S.sub.m1;
S.sub.m2) that detect the length-related mass m.sub.1 and/or the
speed v.sub.1 are arranged before entry into the conditioning
section (AF).
5. The device pursuant to claim 2, wherein the formatting device
(F) comprises a cutting device and that the sensor (S.sub.m2), when
viewed in the moving direction of the filter strand, is arranged
directly in front of the cutting device and that as sensor
(S.sub.v2) the measuring unit for the formatting line speed is
used.
6. The device pursuant to claim 2, wherein the sensors (S.sub.v1;
S.sub.v2) that detect the current speeds v.sub.1 and v.sub.2 of the
continuous filter strand are optical speed sensors.
7. The device pursuant to claim 2, wherein as the sensor (S.sub.m1
and/or S.sub.m2) that detects the length-related mass m.sub.1
and/or m.sub.2, a sensor is selected that is suited to determine
apart from the length-related masses also the moisture content of
the current product to be measured.
8. The device pursuant to claim 2, wherein the sensor (S.sub.m1
and/or S.sub.m2) is a microwave sensor.
9. The device pursuant to claim 8, wherein the microwave sensor is
a split resonator.
10. The device pursuant to claim 8, wherein the microwave sensor
comprises a closed, tube-shaped resonator that is perforated with a
plastic probe guide.
11. The device pursuant to claim 8, wherein the microwave sensor is
designed as a planar sensor.
12. The device pursuant to claim 8, wherein the microwave sensor is
designed as a profile sensor. The device
13. The device pursuant claim 2, wherein the sensor (S.sub.m1
and/or S.sub.m2) that detects the length-related mass m.sub.1
and/or m.sub.2 of the continuous filter strand is a
.beta.-radiation source as well as a .beta.-radiation detector.
14. The device pursuant to claim 1, wherein bale scales are used as
a sensor for determining the mass flow M.sub.1.
15. The device pursuant to claim 1, wherein said device comprises a
regulation unit for the automatic regulation of the filter material
and softener mass, which is coupled at its output both to the
conditioning section (AF) and the dosing section (4).
Description
[0001] The invention relates to a device for the simultaneous,
continuous measurement and regulation of the acetate and triacetin
levels during the production of filter rods, especially for the use
in the tobacco industry.
[0002] Cigarette filters are an essential, quality-relevant part of
cigarettes so that great efforts are undertaken to optimize the
manufacturing method for filter rods when it comes to quality. In
doing so, a most goal-oriented regulation of the method has to be
considered, which of course depends on a most precise and fast
characterization of the product quality. In the optimal case this
is done through an online method.
[0003] For the characterization of filter rods in the tobacco
industry, parameters such as diameter, acetate weight and triacetin
value as well as tractive resistance are evaluated. In determining
the acetate weight, tractive resistance and triacetin content
usually offline procedures are applied. The determination of the
acetate weight is done gravimetrically by evaluating the gross
weight of the rods and by subtracting the mass of the wrapping
paper, adhesive and triacetin. Paper and adhesive amounts are
likewise evaluated in a gravimetric fashion, wherein these are
largely parameters that are irrelevant to the process. In the
determination of the triacetin value different methods are applied.
For one the weight of a defined number of filter rods with and
without triacetin is evaluated. The difference between the two
measurements then results in the triacetin content. This method has
the disadvantage of being feasible only occasionally or resulting
in a high amount of waste when used frequently. Beyond that methods
are available for the evaluation of triacetin in finished filter
rods. By way of example, the extraction of triacetin with a
suitable solvent and the determination of the triacetin content by
a laboratory method such as gas chromatography can be
mentioned.
[0004] Another procedure that could be named is the determination
of the softener content by measuring the reflection of infrared
beams in the near infrared range (see e.g. CANON A. B.; HUGHES I.
W.: On-line measurement of triacetin in cigarette filter rods using
near infrared reflectance spectroscopy); Tob. Chem. Res. Conf.,
1987). This method has the considerable disadvantage of being a
surface measuring method and that the infrared beam penetrates only
a few wavelengths into the product to be measured. This causes the
measurement result to strongly depend on the migration behavior of
the softener, but also on the fineness of the fibers and the
packing density of the employed filter material.
[0005] All these methods have the disadvantage that they only
reflect momentary images of the current production since they are
all performed off-line.
[0006] For this reason on-line determination procedures for acetate
weight, which may also be used for method regulation purposes, have
been used for quite some time now. For example DE 28 15 025
describes the measurement of the density and herewith mass of the
finished filter strand using a beta ray detector. This procedure
thus allows a determination of the mass of the finished filter rod,
wherein the mass in this case is composed successively of the
acetate mass and the applied triacetin quantity. In this procedure
the off-line process described above is employed for the
determination of the triacetin content. With certain restrictions,
the method is also already suited for regulating the overall mass
of the filter rods, but with the limitation that the density
evaluation using a beta ray detector cannot detect moisture
fluctuations in the product to be measured.
[0007] Another quasi on-line determination is described in DE 31 49
670 A1. Here the applied amount of acetate is determined by
positioning the filter tow material on a scale and continuously
recording the consumption of material throughout the manufacturing
process. The simultaneous determination of the number of cuts
(filter rod segments) per time unit allows a conclusion of the
amount of acetate used per filter rod by combining these two
measured variables.
[0008] If in addition to that the end weight of the filter rods is
determined through an external weighing process, the difference
between material used and actual filter rod mass results in the
applied amount of triacetin. This procedure as well has the
disadvantage that it can be referred to as an on-line process only
conditionally since it requires an additional off-line weight
determination of the finished filter rods. The frequency of
triacetin values available with this method is determined by the
frequency of the external gross weight determination processes.
Since for this process in turn filter rods have to be removed from
the product stream, this evaluation is likewise associated with a
considerable amount of waste. In addition, the scale has the
disadvantage that malfunctions occurring from certain tow defects
may not be detected. One of these malfunction factors would be e.g.
the failure of a spinning nozzle during the production process of
the filter tow with the result that for a short time 2 to 5% of the
nominal overall titer is missing. This results in the end in
approx. 2.5% lighter filter rods while using the same amount of
material, measured based on the weight reduction of the bale. As a
result this would provide the incorrect perception of too low a
triacetin content. Additionally, short-term fluctuations as well
the amount of acetate and the amount of triacetin cannot be
determined with the help of this method.
[0009] Another disadvantage of this procedure is that in the
determination of the acetate quantity the moisture level of said
acetate is not taken into consideration. The equilibrium moisture
content of cellulose acetate under normal conditions is approx.
5.5% by weight. Under conventional production practices the
starting moisture of a filter tow may vary between approx. 3.5 and
7% by weight due to modified process parameters. This variation
results in a relative inaccuracy of the afore-mentioned weight
evaluations for the triacetin and acetate amounts. To complete the
picture it shall also be mentioned here that the end moisture level
and therewith the gross weight of the finished filter rods can be
influenced significantly by changing process parameters during
filter rod production. By way of example parameters such as room
climate, processing speed and the temperature and moisture level of
the air on the spreading nozzles shall be mentioned.
[0010] The present invention is based on the object of eliminating
the above-mentioned disadvantages of the state of art and
describing a device for the simultaneous, continuous measurement of
acetate and triacetin masses and the regulation of the production
process.
[0011] Pursuant to the invention the object is achieved with a
device pursuant to claim 1. The device pursuant to the invention
for the production of cigarette filters with simultaneous
regulation of the filter material and softener compound, comprising
a conditioning section AF for conditioning of the supplied filter
tows, a formatting device F for producing a wrapped filter strand,
and a dosing device integrated into the conditioning section for
dosing a softener compound, is characterized in that the device
furthermore comprises sensors that detect the mass flow of filter
tow material M.sub.1 and sensors that detect the sum of the mass
flow from filter tow material and softener compound M.sub.2,
wherein the device contains a measuring and regulation unit that is
coupled with the sensors for measuring the mass flows (M.sub.1 and
M.sub.2) in such a manner that both the filter material and the
softener compound can be measured and regulated independently.
[0012] In a preferred embodiment of the invention, viewed in the
moving direction of the filter strand, sensors S.sub.m1, S.sub.m2
for detection of the length-related mass m.sub.1, m.sub.2 of the
continuous filter strand and sensors S.sub.v1, S.sub.v2 for
detection of the current speeds v.sub.1 and v.sub.2 of the
continuous filter strand are located in front and after the
softener dosing unit, wherein each mass flow results from the
product from m.sub.1.times.v.sub.1=M.sub.1 and
m.sub.2.times.v.sub.2=M.sub.2.
[0013] In general the employed sensor S.sub.m1, S.sub.m2, S.sub.v1
and S.sub.v2 may be arranged in different locations of the overall
device, wherein it is essential for the invention that the sensors
marked with "1" are always located in front of the dosing unit and
the sensors marked with "2" after the same, when viewed in the
moving direction of the filter strand. The first mass sensor
S.sub.m1 and speed sensor s.sub.v1 may thus be located at any given
point between the bale feed area and the dosing unit.
[0014] In a beneficial embodiment the sensor S.sub.v1 for detection
of the speed v.sub.1 and the sensor S.sub.m1 for detection of the
length-related mass m.sub.1 are arranged directly adjacent.
[0015] "Directly adjacent" should be understood such that they are
located directly behind one another in the moving direction of the
filter strand without another element of the device being located
between them. If the sensors work touch-less, it may be possible,
if necessary, to measure at the same location. This ensures that
speed and length-related mass are measured at one point of the
filter strand where identical overall conditions regarding the
drawing condition of the filter tows prevail.
[0016] For reasons of measuring sensitivity, especially regarding
sensor S.sub.m1, it has proven especially favorable if the mass
flow M.sub.1 is evaluated before the filter tow enters the
conditioning unit AF.
[0017] In another beneficial embodiment of the invention the sensor
S.sub.m2 is placed directly in front of the cutting device, viewed
in the moving direction of the filter strand, and as sensor
S.sub.v2 the measuring unit for the formatting line speed is
applied.
[0018] The speeds v.sub.1 and v.sub.2 are preferably determined
with optical sensors. Such optical sensors have the advantage that
measurement of the relative speed between two objects can be done
touch-less. In doing so, no mechanical interference with the motion
of the filter strand takes place. On such optical sensors the
surface structures of the filter strand are typically projected on
a grid, where they create light modulation. With the help of a
photoelectric element, this light modulation is converted into a
frequency that is proportional to the relative speed. Other
possibilities for touch-less measurement of the speed of a
continuous material strand are feasible, but are not mentioned
here.
[0019] In principle any sensor that allows the direct or indirect
detection of the length-related mass of a continuous material
strand may be used as a "mass sensor".
[0020] It is particularly beneficial if apart from the
length-related mass also the moisture content of the product to be
measured can be determined, simultaneously and independently from
the mass determination, since only this way a complete mass
assessment can be performed during the production process
(moisture, acetate-triacetin mass).
[0021] Therefore preferably microwave resonators that are used as
mass sensors are employed determine the length-related mass m.sub.1
and m.sub.2.
[0022] EP 0 468 023 B1 explains how by measuring two physical
effects the length-related mass and the moisture of a product that
is located in the microwave field of a microwave resonator can be
determined independently from each other. Microwave resonators
create a standing wave with the resonance frequency, through which
the acetate and/or filter material is moved with the aid of special
openings and with product guides lined with dielectric material.
Through this special interaction between the standing microwave and
the product, the resonance characteristics of microwave resonators
are modified. A great advantage of these resonators is that
adaptations to a variety of applications are possible through the
geometric layout and that this way a large measuring effect and a
great penetration depth into the product can be achieved. Moreover,
contrary to measuring techniques that do not use the principle of
resonance (such as the irradiation or stray measuring techniques),
measuring the loss of microwave energy resulting from the
absorption into the product has the quality of an exact measured
value, which is not given with irradiation measurements due to
leakage losses that cannot be determined. The afore-mentioned
patent publication provides an entire list of examples for such
resonators: For extensive material shapes, as those of the filter
tow strand in the entire region of the conditioning section (AF)
before the dosing unit, a sensor type whose microwave measurement
field can be designed very homogeneously in a measuring gap that is
up to 3 cm wide and up to 30 cm long is particularly suited so that
the position of the product in the sensor does not matter for the
strength of interaction between the microwaves and the product.
This "split resonator" is a resonator that is excited in the basic
mode of E.sub.010 and that was cut open in the direction of the
wall currents, resulting in a measuring zone with an extremely
homogeneous measuring field.
[0023] For a lateral one-sided measurement of the acetate strand
before application of the softener compound a planar sensor is also
suited, comprising a standing wave over a planar surface, the
leakage field of which extending from the sensor surface decreases
into the space exponentially up to a maximum expansion of 10 cm.
Such a sensor is described in EP 0 908 718.
[0024] In front of the first spreading nozzle, before the filter
tow material is aligned to an extensive strand, it is also possible
to use a closed resonator, which is perforated with a plastic probe
guide and is excited in the E010 basic mode, thus having a maximum
measuring field, i.e. maximum sensitivity, in the probe area.
[0025] In the area of the filter strand after application of the
softener compound, position Sm.sub.2, the profile sensor is
particularly suited; with it especially a high local resolution of
below 3 mm in the direction of the filter strand can be reached,
and beyond that it is very well suited for measuring the
homogeneity of the softener compound application. Such a profile
sensor is disclosed for example in EP 0 889 321. Said sensor
comprises a through-hole at a right angle to its area extension.
The through-hole is delimited by metallic walls extending in the
longitudinal direction and is essentially flat. Said resonator is
preferably filled with a dielectric. Its thickness is considerably
less than its lateral dimensions, i.e. less than the traverse
dimension perpendicular to the thickness.
[0026] The particular advantages of a microwave sensor with respect
to the beneficial embodiment pursuant to claim 8 shall be explained
in more detail here. In the case of the microwave resonator
measuring technique there are two variables that are direct
measured variables: the change in resonance frequency A and the
increase in the half-width value B of the resonance curve over the
resonator at empty. The first effect of the resonance frequency
increment A depends above all on the shortening of the wavelength
by the dielectric product that is currently located in the
measuring field of the resonator (i.e. on the so-called real part
of the dielectricity constant). The second effect B is caused by
the conversion of microwave energy into heat, which can be measured
only accurately with the resonator method (the "microwave oven
effect" or the so-called imaginary part of the dielectricity
constant). Since both variables are equally proportional to the
mass of the product in the measuring field, both are also suited
for mass measurement. In principle parameter A is used for this. On
the other hand both measured variables are dependent in different
fashions is on the moisture level. Thus the quotient of both
variables B/A supplies a mass-independent measured variable that is
dependent only on moisture and can be calibrated against the
material moisture level. With this variable on the other hand the
influence of moisture on the mass value A can be compensated for so
that two independent measured variables can be provided: moisture,
which is independent from mass, and mass, which is independent from
moisture. Moreover the moisture information of the incoming acetate
strand can be utilized to compensate for moisture fluctuations
among the different acetate bales as well as within the bale by
regulating the mass flow.
[0027] A great advantage of the microwave measuring method is the
constancy of the performed calibration and its independence from
fluctuations of material parameters, such as e.g. the change in
manufacturing parameters for acetate, e.g. its overall titer or its
thread strength. The measuring method has recently been optimized
so as to achieve a very high measuring speed and precision, and now
after 0.1 milliseconds a new moisture and mass value can be issued,
respectively, i.e. 10,000 values per second.
[0028] Alternatively density measurements can also be performed by
means of beta radiation. And finally also an optical sensor, on
which the density is detected by means of stray light measurements
with infrared radiation, can be used as a mass sensor. These
sensors are well known to those skilled in the area of metrology
and should therefore not require further explanations. The last two
methods, however, have the disadvantage that they do not detect the
moisture of the filter tow so that the triacetin determination is
subject to greater inaccuracy than in the case of the microwave
method.
[0029] Pursuant to another preferred embodiment of the invention
the mass flow M.sub.1 can also be determined by means of bale
scales pursuant to DE 31 49 670 A1, wherein the previously
mentioned limitations with respect to moisture assessment
apply.
[0030] Pursuant to the invention the output signals of all sensors
are fed either to a regulation unit and/or a display unit. If a
regulation unit is present, an automatic regulation of the method
that is conducted with the device pursuant to the invention may be
performed, which is especially beneficial under production
conditions. Alternatively it is also possible for an operator to
personally record the signals that are depicted with the display
unit and perform the corresponding regulation. When both
afore-mentioned features are available, a control of the automatic
regulation may be conducted with the display unit.
[0031] In a beneficial embodiment, the regulation unit is coupled
with the drive unit of the conditioning section (AF) and the gear
pump, which supplies the dosing device with the required quantity
of triacetin.
[0032] The operating principle of the inventive device will be
explained in the following in more detail with reference to the
attached drawing. The only FIGURE in the drawing shows an
embodiment of a device pursuant to the invention for the production
of cigarette filters.
[0033] A conventional filter rod machine, as it is known from the
prior art, operates as follows:
[0034] The filter tow that is supplied to the filter rod machine is
pulled from a bale 8 and fed into the conditioning section (AF) via
a so-called boom 9. In front of the spreading nozzle 3" the sensors
S.sub.v1 and S.sub.m1 are arranged in sequence next to each
other.
[0035] The conditioning section (AF) generally comprises two
spreading nozzles 3 and 3', a pair of brake rollers 1, which
pre-draw the filter strand, as well as pairs of drawing rollers 2,
which operate at different speeds and subject the filter strand to
a drawing process. The drawing rollers can be equipped with a
thread-like surface so that only parts of the-spread filter strand
passing through are seized and drawn. This way the individual
filament groups, which make up the filter strand, are shifted in
relation to each other. Moreover the conditioning section comprises
a pair of deflection rollers 5 at its output, by means of which the
conditioned filter strand is deflected in a direction that is
suitable for entry into the feed nozzle and the feed fingers of the
downstream formatting device F.
[0036] The drawing rollers 2 as well as the deflection roller 5 are
driven rollers, which are driven in relation to one another at a
fixed speed ratio.
[0037] In the downstream formatting device F the filter strand is
gathered to the diameter of the future cigarette filter, wrapped
with paper, and subsequently the filter rods are cut to the
required length in a cutting device 7. The sensor S.sub.m2 is
arranged directly in front of the cutting device 7. A textile belt,
called a formatting line, which firmly encloses the filter strand
during the gluing operation, is used as mentioned above as the
conveying means for the filter strand. As already mentioned, the
speed of said conveying means corresponds to the speed of the
filter strand in the formatting device and hence past the dosing
device 4. Said speed is measured with the sensor S.sub.v2.
[0038] Metering of the acetate mass takes place in the filter rod
machines pursuant to the prior art by modifying the difference in
speed between the conditioning section (AF) and the formatting
section (F), wherein generally that of the formatting section (F)
is kept constant.
[0039] The acetate mass, however, can also be varied with other
measures. EP 0 629 356 B1 for example describes the regulation of
the acetate mass by modifying the brake roller pressure on the pair
of brake rollers 1.
[0040] The dosing device 4 is preferably arranged between the
drawing rollers and the deflection rollers in the conditioning
section. The softener is hence applied on the completely spread
filter strand. The dosing device generally consists of an atomizing
housing, in which for example rotating brushes are arranged, which
serve the fine atomization of the softener compound and its
dispersion onto the spread fiber strand. Generally triacetin or
TEGDA (triethylene glycol diacetate) are used as the softener
compounds. A complete list of possible softeners can be found in DE
19951062 A1.
[0041] The quantity of softener that is required for this process
is generally fed to the dosing device 4 by means of a gear pump.
Metering of the softener quantity hereby occurs through a change in
the rotational speed of the drive unit of said gear pump.
[0042] The device pursuant to the invention enables a simultaneous
regulation of the filter material and/or acetate quantity and of
the softener quantity during the production of filter rods.
[0043] Generally it is true that the mass flow of filter tow
material in all areas of the device is constant. The following is
true for the products M.sub.1 and M.sub.2 from mass and speed as
long as no softener is used:
M.sub.1=M.sub.2
[0044] As soon as a softener is used:
M.sub.1<M.sub.2,
[0045] wherein the difference between M.sub.1 and M.sub.2
represents a measure for the amount of softener per filter rod.
[0046] The following applies:
W=K.times.(M.sub.2-M.sub.1)+C,
[0047] wherein W is the amount of softener in mg per filter rod,
and K and C are factors that are determined by calibration. These
calibration factors are variables that result from the sensor
characteristic.
[0048] Calibration hence makes it not only possible to regulate the
softener content per filter rod, but also to measure it
quantitatively continuously, regardless of the filter tow
specification that is used.
[0049] A similar rule applies for the mass of used filter tow
material M per filter rod. It has a linear dependency on the
product M.sub.1.
[0050] The following applies:
M=K.sub.1M.sub.1+C.sub.1,
[0051] wherein K.sub.1 and C.sub.1 in turn have to be determined by
calibration in accordance with the sensor characteristic.
[0052] A regulation that is performed with the device pursuant to
the invention should be performed such that the products M.sub.1
and M.sub.2 are each kept constant.
[0053] In practice it has turned out that during regulation
essentially three cases may arise:
[0054] 1. At a constant speed of the conditioning section (AF) and
the formatting section (F) the product M.sub.2 changes while
M.sub.1 remains the same. This is a sign that too little or too
much softener was added. In this case the rotational speed of the
gear pump of the dosing device must be adjusted such that the
product M.sub.2 is returned to the original quantity.
[0055] 2. Both the product M.sub.1 and the product M.sub.2 change
and the signal of the speed sensor S.sub.v1 remains constant, while
the signal S.sub.m1 changes. In this case a thread breakage has
occurred. This means the failure of a spinning nozzle during the
manufacturing process of the filter tow with the consequence that
in the short term 2 to 5% of the nominal overall filter is missing.
For the expert the effects of such a malfunction are clearly
foreseeable. Without regulation, this will lead to a drop in the
acetate content of the filter rod, associated with decreased
tractive resistance.
[0056] 3. Both the product M.sub.1 and the product M.sub.2 change,
wherein the signal of the speed sensor S.sub.v1 changes and
S.sub.m1 remains constant. In this case the cause is a change in
the crimping index of the filter strand. This failure as well leads
without regulation to a change in the acetate content of the filter
rod and in the tractive resistance, as is clearly detectable for
those skilled in the art.
[0057] In the latter two cases the speed of the conditioning
section (AF) should be adjusted such that the product M.sub.1 is
returned to the original value.
[0058] Of course in theory all three cases can also occur
simultaneously. In this very unlikely case, M.sub.1 will first be
returned as described to the original value and subsequently
another regulation as described in case 1 will be performed for
M.sub.2.
[0059] With some additional calculations also a product-related and
process-related moisture correction can be performed with the use
of microwave sensors, as mentioned above. For this, however, it
will be required to prepare sensor-specific calibration curves. A
more detailed illustration of the method is foregone at this
point.
[0060] In the case of a thread breakage (case 2), the regulation
can be designed, likewise with some additional calculations, such
that it is not a constant acetate weight that is achieved as the
target variable, but a constant tractive resistance. This type of
regulation presupposes that the dependencies of tractive
resistance, acetate weight and overall titer are known. Such
calculation models exist. One of them is marketed by Rhodia Acetow
under the name "Cable.COPYRGT.".
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